U.S. patent number 5,486,181 [Application Number 08/286,003] was granted by the patent office on 1996-01-23 for acetabular cup, method and tool and installing the same.
This patent grant is currently assigned to Implex Corporation. Invention is credited to Robert C. Cohen, Rafial Zubok.
United States Patent |
5,486,181 |
Cohen , et al. |
January 23, 1996 |
Acetabular cup, method and tool and installing the same
Abstract
An acetabular cup having an outer shell of a hard material
defining a cavity circumscribed by an annular surface, and a
bearing insert of a material which is softer than the material of
the outer shell, the bearing insert being disposed within the
cavity of the shell, and coupling tracks disposed on the annular
surface for coupling a tool to the outer shell, the tool being used
for installing the cup in a patient's acetabulum, the coupling
tracks operating to prevent the tool from damaging the bearing
insert during the installation of the cup. The tool for installing
the acetabular cup of the present invention, comprises a handle for
aligning and driving the acetabular cup into a patient's acetabulum
which control the rotational, pivotal and axial alignment and an
adaptor for coupling the handle to the acetabular cup, the adaptor
having leg members for engaging the corresponding coupling tracks
positioned on the annular surface of the outer shell when the leg
members are brought into contact with the annular surface of the
outer shell and the adaptor is rotated relative to the acetabular
cup.
Inventors: |
Cohen; Robert C. (Rockaway
Township, NJ), Zubok; Rafial (Midland Park, NJ) |
Assignee: |
Implex Corporation (Allendale,
NJ)
|
Family
ID: |
23096630 |
Appl.
No.: |
08/286,003 |
Filed: |
August 4, 1994 |
Current U.S.
Class: |
606/91; 606/99;
606/100 |
Current CPC
Class: |
A61F
2/34 (20130101); A61F 2/4609 (20130101); A61F
2220/0025 (20130101); A61F 2002/30881 (20130101); A61F
2002/30322 (20130101); A61F 2230/0019 (20130101); A61F
2002/30883 (20130101); A61F 2002/30968 (20130101); A61F
2220/0033 (20130101); A61F 2002/342 (20130101); A61F
2/30767 (20130101); A61F 2002/3456 (20130101); A61F
2250/0019 (20130101); A61F 2002/30387 (20130101); A61F
2310/00029 (20130101); A61F 2/4612 (20130101); A61F
2002/30112 (20130101); A61F 2250/0026 (20130101); A61F
2002/3082 (20130101); A61F 2310/00023 (20130101); A61F
2002/30378 (20130101); A61F 2002/30879 (20130101); A61F
2230/0004 (20130101); A61F 2002/30337 (20130101); A61F
2002/30153 (20130101); A61F 2250/0087 (20130101); A61B
17/86 (20130101); A61F 2002/3443 (20130101); A61F
2/4603 (20130101); A61F 2002/3071 (20130101); A61F
2002/30016 (20130101); A61F 2310/00952 (20130101); A61F
2002/3406 (20130101); A61F 2310/00413 (20130101) |
Current International
Class: |
A61F
2/32 (20060101); A61F 2/34 (20060101); A61F
2/46 (20060101); A61B 17/68 (20060101); A61B
17/86 (20060101); A61F 2/00 (20060101); A61F
2/30 (20060101); A61F 002/46 (); A61B 017/88 () |
Field of
Search: |
;606/91,99,100,86
;623/22 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Willse; David H.
Assistant Examiner: Snow; Bruce E.
Attorney, Agent or Firm: Plevy & Associates
Claims
I/We claim:
1. A tool for installing an acetabular cup having an outer shell of
a hard material with a cavity circumscribed by a peripheral
surface, and a bearing insert of a material which is softer than
said material of said outer shell disposed within said cavity of
said shell, said tool comprising:
handle means for aligning and driving the acetabular cup into said
acetabulum;
adaptor means for coupling said handle means to said acetabular
cup, said adaptor means having leg means for engaging corresponding
leg receiving means positioned on the peripheral surface of the
outer shell when said leg means are brought into contact with the
peripheral surface of the outer shell and said adaptor means is
rotated relative to said acetabular cup, said leg means including a
pair of substantially parallel oriented leg members unitarily
formed with said adaptor means, and locking means for preventing
relative rotation between said adaptor means and the acetabular cup
when said leg means of said adaptor means are engaged with the leg
receiving means of the outer shell, said locking means being
slidably oriented between said pair of leg members.
2. The tool according to claim 1, wherein said handle means
includes release means for deactivating said locking means of said
adaptor means and allowing relative rotation between said adaptor
means and the acetabular cup so that said legs means of said
adaptor means can be disengaged form the leg receiving means of the
outer shell.
3. The tool according to claim 1, wherein said handle means further
includes assist handle means for aligning said cup within said
acetabulum.
4. The tool according to claim 1, wherein said adaptor means
further includes chuck means and said handle means further includes
chuck receiving means, said chuck means on said adaptor means and
said chuck receiving means on said handle means coacting to couple
and uncouple said adaptor means and said handle means.
5. The tool according to claim 1, wherein said adaptor means
further includes indicia means, said indicia means allowing said
adaptor to be selectively matched by size with a corresponding
acetabular cup.
Description
FIELD OF THE INVENTION
The present invention relates generally to an improved prosthetic
device, and more particularly to an improved acetabular cup
assembly and method which facilitates implanting the cup in a
patient's acetabulum as a fully assembled unit. Additionally, the
invention relates to a tool for installing the acetabular cup
assembly of the present invention.
BACKGROUND OF THE INVENTION
To allow a wide range of motion at the hip, the joint is configured
as a ball and socket arrangement. These joints provide for a wide
range of motion. In a hip joint, the femoral head is joined to the
proximal femur by a neck which is angularly disposed relative to
the axis of the femur. The natural socket or acetabulum located in
the pelvis, receives the femoral head and cooperates with it to
form a joint which permits relative motion. Deterioration of the
acetabulum and/or femoral head can be brought about by injury or
various progressive diseases such as osteoarthritis. When injury or
disease occurs, the damaged component can be replaced or rebuilt
using an appropriate prosthetic device. Various techniques have
been developed over the years for replacing injured or deteriorated
joint components. In the technique known as a "total hip
replacement", one method involves cementing or press-fitting a cup
into the acetabulum. In this technique, the entire natural femoral
head and neck are removed and a femoral prosthetic device
comprising an elongated stem, a neck and a bearing head is
implanted within the proximal femur.
In any event, acetabular implants are well known in the an for
replacing the socket portion of a patient's hip joint. Typical
acetabular cup assemblies comprise a metal cup shell which are
adapted to be secured within the patient's acetabulum, and an inner
liner of plastic material which provides a spherical bearing
surface for receiving the femoral bearing head portion of the
femoral prosthetic device. The metal cup shell may be provided with
an external thread arrangement to facilitate anchoring to the
pelvic bone or it may be secured by other means such as cement,
screws or simply an interference fit. The plastic insert can be
secured within the metal cup in a variety of methods which include
using retaining rings, press fitting or force fitting the plastic
insert into the interior of the metal cup and/or thermally fitting
the plastic insert into the interior of the metal cup.
A particular problem that can occur with prior art acetabular cup
designs is that they can be damaged by the tools used for impacting
or driving them into the acetabulum. This is especially true
regarding acetabular cup designs having the plastic bearing insert
already installed into the metal shell prior to the cup being
implanted into the acetabulum.
In partial or total hip replacement surgery utilizing this type of
acetabular cup, the surgeon places the impaction tool used for
positioning and driving the cup into the acetabulum, onto the metal
shell or onto the plastic insert.
In the case where the tool is placed on the metal shell slippage of
the impaction tool can occur if the metal shell has no provision
for receiving the impaction tool. If the impaction tool slips off
the metal shell it can damage the plastic bearing insert. Once the
bearing insert is damaged, the surgeon may have to replace it
and/or remove and replace the entire cup which is quite costly and
time consuming. Moreover, since the impaction tool is not securely
coupled to the acetabular cup, it may be difficult to properly
orient the acetabular cup in the acetabulum during impaction. This
presents a serious problem because in order to realize maximum
performance from this surgical procedure, the acetabular cup must
be properly positioned in the acetabulum. If the acetabular cup is
incorrectly implanted, dislocations of the hip joint, decreased
range of motion, and eventual loosening or failure of the
prosthetic components can occur.
In the case where the impactor tool is placed onto the plastic
insert, the impactor may cause permanent deformation and provide
for less than optimum contact with the femoral prosthetic bearing
head. This can result in accelerated generation of poly debris due
to poor contact and a disturbance of the plastic insert locking
mechanism.
The present invention overcomes these problems by providing means
for coupling a specially designed cup impactor tool to the
acetabular cup.
It is, therefore, an object of the present invention to provide an
improved acetabular cup design, method and tool for installing the
cup which allows the acetabular cup to be installed in the correct
orientation and as an assembled unit without damaging the plastic
bearing insert.
SUMMARY OF THE INVENTION
The present invention comprises an acetabular cup having an outer
shell of a hard material defining a cavity circumscribed by an
annular surface, and a bearing insert of a material which is softer
than the material of the outer shell, the bearing insert being
disposed within the cavity of the shell, and coupling means
disposed on the annular surface for coupling a tool to the outer
shell, the tool being used for installing the cup in a patient's
acetabulum, the coupling means operating to prevent the tool from
damaging the bearing insert during the installation of the cup.
The present invention further includes a method for implanting the
acetabular cup of the present invention into a patients's
acetabulum, the method comprising the steps of preparing the
acetabulum to receive the cup, attaching an installation tool to
tool coupling means on the outer shell of the cup, aligning the cup
within the acetabulum using the installation tool which provides
for a means to control rotation, axial alignment impacting
direction, and pivotal orientation, driving the cup into the
acetabulum using the installation tool, and detaching the
installation tool from the outer shell by actuating a tool
releasing means located on the installation tool.
The present invention also includes a tool for installing the
acetabular cup of the present invention, comprising handle means
for aligning and driving the acetabular cup into a patient's
acetabulum, adaptor means for coupling the handle means to the
acetabular cup, the adaptor means having leg means for engaging
corresponding leg receiving means positioned on the peripheral
surface of the outer shell when the leg means are brought into
contact with the peripheral surface of the outer shell and the
adaptor is rotated relative to the acetabular cup.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a cross-sectional view of a preferred exemplary
embodiment of the acetabular cup of the present invention,
(impactor tool coupling means not visible in this view);
FIG. 2A is a cross-sectional view of the outer shell member of the
acetabular cup of FIG. 1 with the bearing insert removed;
FIG. 2B is an enlarged view of the locking track shown in FIG.
2A;
FIG. 2C is a cross-sectional view through the locking track shown
in FIG. 2B;
FIG. 2D is a side plan view of the outer shell member shown in FIG.
2A;
FIG. 2E is a bottom plan view of the outer shell member of FIG.
2A;
FIG. 3 is a cross-sectional view through the bearing insert which
is installed in the acetabular cup shown in FIG. 1;
FIG. 4A is a cross-sectional view through a preferred exemplary
embodiment of the cup adaptor of the present invention;
FIG. 4B is a cross-sectional view through the body of the cup
adaptor shown in FIG. 4A;
FIG. 4C is a partial cross-sectional view of the pivoting locking
leg of the cup adaptor of FIG. 4A;
FIG. 4D is a bottom plan view of the cup adaptor shown in FIG.
4A;
FIG. 4E is a top plan view of the cup adaptor shown in FIG. 4A;
FIGS. 4F and 4G are side elevational views of the cup adaptor shown
in FIG. 4A;
FIG. 5A is a plan view of the a preferred exemplary embodiment of
the impactor tool of the present invention;
FIG. 5B is a cross-sectional view through the coupling means of the
of the impactor tool shown in FIG. 5A;
FIGS. 5C and 5D are cross-sectional views which show how the
coupling means of the impactor tool couples to the chuck of the cup
adaptor;
FIGS. 6A-6C show how the cup adaptor attaches to the locking track
of the acetabular cup;
FIG. 6D is a cross-sectional view of FIG. 6A along line D--D;
FIG. 7A is a partial cross-sectional assembled view of acetabular
cup, cup adaptor and impactor tool;
FIG. 7B shows how the cup adaptor/impactor tool of FIG. 7A is
disengaged from the acetabular cup.
DETAILED DESCRIPTION OF THE INVENTION
Referring to FIG. 1, there is shown a cross-sectional view of a
preferred embodiment of an acetabular cup according to the present
invention designated by the numeral 10. Generally, the acetabular
cup 10 is a two component assembly comprising a shell component 12
and a bearing insert 60 which has been assembled within the shell
component 12. Preferably, the shell component 12 is made from a
metal such as titanium or cobalt-chrome alloy, however, any
material which is compatible with the bone and body tissues of the
patient can be used. The bearing insert 60 is preferably made from
a plastic material such as polyethylene or any other like
biocompatible bearing material which has sufficient strength and
wear resistance.
The structure of the shell component 12 will now be described in
greater detail with reference to FIG. 2A. As can be seen, the
exterior of the shell component 12 comprises an apical region 14, a
rim region 16, and a small base region 18.
The surface curvature of the apical region 14 is preferably
ellipsoidal, however, any suitable profile such as hemispherical or
the like, is contemplated. Acetabular cups having ellipsoidal
surface curvatures are described in U.S. patent application Ser.
No. 08/052,248 entitled PROSTHETIC ACETABULAR CUP AND METHOD OF
IMPLANT, filed on Apr. 22, 1993 by Robert Averill et al. and
assigned to Implex Corporation, the assignee herein, the disclosure
of which is incorporated herein by reference.
A plurality of locking ribs 20 are provided along the rim region 16
of the shell component 12. The locking ribs 20 are arranged in
parallel rows and are coaxially positioned around the mid-axis 19
of the shell component 12. A transition rib 22 is disposed on the
shell component 12 at the top of rim region 16. The transition rib
22 is also arranged in parallel with the locking ribs 20 and is
co-axially positioned around the mid-axis 19 of the shell component
12. Preferably, each of the locking ribs 20 have a generally dove
tail shape profile in cross-sectional the details of which are also
described in U.S. patent application Ser. No. 08/052,248.
The base region 18 of the shell component 12 includes a vertical
surface 26 that extends below the lower most locking rib 20 to a
chamfered edge 24. Chamfered edge 24 joins the vertical surface 26
to the horizontal annular base surface 28 of the shell component
12.
Disposed on the horizontal annular base surface 28 are impactor
tool coupling means. In the preferred embodiment shown in FIGS.
2A-2E, the impactor tool coupling means comprises a pair of locking
tracks 42A and 42B. The locking tracks are disposed approximately
180 degrees apart on the horizontal annular base surface 28 of the
acetabular cup as shown in FIGS. 2D and 2E. It should be
understood, however, that any suitable number of locking tracks can
be provided on the annular base surface of the acetabular cup.
Moreover, many variations in the structure of the locking tracks
shown in the preferred embodiment of FIGS. 2A-2E, are possible.
Referring now to FIG. 2B, which shows an enlarged view of locking
track 42A and FIG. 2E which shows both locking tracks 42A and 42B,
the locking tracks will now be described in detail. Locking track
42A includes a first inclined ramp surface 48A which emerges from
the horizontal annular base surface 28 and extends
circumferentially into a track rim surface 46A. The track rim
surface 46A extends circumferentially in parallel relationship to
the horizontal annular base surface 28 and includes a depression
44A. The track rim surface 46A terminates at a second inclined ramp
surface 49A which merges back into the horizontal annular base
surface 28.
Similarly, as is visible in FIG. 2E, locking track 42B includes a
first inclined ramp surface 48B which emerges from the horizontal
annular base surface 28 and extends circumferentially into a track
rim surface 46B. The track rim surface 46B extends
circumferentially in parallel relationship to horizontal annular
base surface 28 and includes a depression 44B. The track rim
surface 46B terminates at a second inclined ramp surface 49B which
merges back into the horizontal annular base surface 28. Referring
to FIG. 2C, locking track 42A further includes an inner undercut
surface 50A and an outer surface 52A which is a continuation of
vertical surface 26.
The locking tracks operate to allow the acetabular cup to be
securely coupled to the impactor tool at the outer periphery of the
shell component 12. This configuration assures that the impactor
tool will not damage the bearing insert of the acetabular cup as it
substantially eliminates slippage between the shell component and
the impactor tool during the installation of the cup. Further, the
secure coupling of the acetabular cup to the impactor tool allows
the surgeon to precisely orient the acetabular cup in the patient's
acetabulum, thus maximizing the performance of the prosthesis.
Moving now to the interior of the shell component 12 and with
reference again to FIG. 2A, there is shown an apex region 30 which
presents a flat surface. Descending from the flat apex region 30 is
a spherically curved surface 32. The bottom of the spherically
curved surface 32 terminates at an annular groove 34 formed in the
shell component 12. Moving below annular groove 34 is a converging
engagement wall 36. A vertical wall 38 extends from the bottom of
the converging engagement wall 36. The vertical wall 38 is parallel
to mid-axis 19. Locking projections 40 extend inwardly from the
bottom of the vertical wall 38 proximate the horizontal annular
base surface 28 of the shell 12.
Referring to FIGS. 1 and 3, it can be seen that the bearing insert
60 generally conforms to the inner surface of the shell component
12. Accordingly the flat top region 62 of the bearing inserts 60
lays flush against the flat apex region 30 within the shell
component 12. Similarly, the spherically curved region 64 of the
bearing insert 60 conforms to the spherically curved surface 32
within the shell component 12. The inclined surface 66 of the
bearing insert 70 lies against the converging engagement wall 36 of
the shell component 12. Although the bearing insert 60 may be
pressed into the shell component 12 the preferred method of
assembly consists of cold inserting bearing insert 60 within the
shell component 12 by creating a temperature differential between
the bearing insert 60 and the shell 12 prior to insertion. By
cooling the bearing insert and/or heating the shell component the
bearing insert can be inserted into the shell without an
interference. Upon an equilibrium in temperature between the
bearing insert and the shell, an interference fit occurs across all
surfaces and the locking projections cut into the material of the
bearing insert locking the bearing insert into a set position
relative to the shell component 12.
Screw holes 25 as shown in FIG. 2D may be provided in the shell
component 12 to aid in securing the shell component in the
acetabulum. The exterior surface of the shell component 12 can also
include a sintered porous coating of beads made from cobalt
chromium or the like which provides for the ingrowth of bone
material into the surface of the shell component to further secure
the shell component in the acetabulum.
As earlier mentioned, the acetabular cup 10 is installed by
coupling it to a novel impactor tool. This is accomplished by
coupling a specially designed cup adaptor between the impactor tool
and the acetabular cup 10. This method allows differently sized
acetabular cups to be installed using the same impactor tool. This
is facilitated by varying the size of the cup adaptors to match and
fit a particular sized acetabular cup. The impactor tool coupling
portion of each cup adaptor, however, is universally sized so that
only one impactor tool required. The cup adaptors are color coded
to match the color code on their respective acetabular cups.
Further, unlocking means are provided in the cup adaptor of the
present invention which coact with corresponding unlocking means
provided on the impactor tool (to be described later on), which
allow the cup adaptor to be remotely uncoupled from the acetabular
cup by actuating the unlocking means provided on the impactor
tool.
In any event, a preferred embodiment of the cup adaptor will now be
described, although, many other embodiments of the cup adaptor are
possible and will become apparent from the foregoing
description.
Referring to FIG. 4A, there is shown a cup adaptor according to a
preferred embodiment of the present invention designated by the
numeral 80. Cup adapter 80 comprises an adapter body 82 have a
centrally disposed axis 94. Extending radially away in opposite
directions from adapter body 82 are leg 84 and split leg 86. Leg 84
comprises an outwardly extending member 85 and a track coupling
section 88. The outwardly extending member 85 extends radially away
from the adaptor body 82. Located at the outer-most portion of
outwardly extending member 85 is the track coupling section 88
which includes a track coupling groove 90.
Similarly split leg 86 includes a pair of parallel oriented
outwardly extending members 87A and 87B (87B not visible in FIG.
4A) which extend radially away from the adaptor body 82. Located at
the outer-most portion of the outwardly extending members is and a
track coupling section 92. As shown in FIGS. 4D and 4E, track
coupling section 92 comprises of a pair of track coupling sections
93A and 93B which correspond to outwardly extending members 87A and
87B. Each track coupling section 93A and 93B defines a respective
track coupling groove 95A and 95B.
Referring again to FIG. 4A, cup adaptor 80 further comprises a
radially extending pivoting locking leg 116 which extends parallel
to and follows the contour of split leg 86. The pivoting locking
leg 116 comprises a body portion 118 which pivotally couples the
locking leg 116 within the adaptor body 82 via a pivot pin 131. An
outwardly extending member 120 extends radially away from body 118.
Disposed at the outer-most end of outwardly extending member 120 is
a locking pin 122.
An impactor coupling chuck 96 extends from adaptor body 82 along
axis 94. Chuck 96 comprises cylindrical member 98. An annular
groove 100 is disposed at the marginal end of cylindrical member
98. Groove 100 defines an annular surface 100A which tapers
outwardly toward the outer most end of cylindrical member 98.
Groove 100 merges into an annular locking flange 102 which is
provided at the outer most end of cylindrical member 98. The outer
most edge of flange 102 presents a chamfered surface 104.
Chuck 96 further includes a bore 106 which extends entirely through
chuck 96 into the adaptor body 82 where it communicates with a
larger bore (not visible in FIG. 4A). The opening on the chuck side
of bore 106 includes a tapered surface 108 which tapers inwardly in
the direction of the adaptor body 82.
A pivoting leg actuating pin 134 resides partially within bore 106
and comprises a shaft portion 136 which is capable of reciprocal
movement within bore 106, and a head portion 138. Actuating pin 134
is designed to engage the body portion 118 of the pivoting locking
leg 116 via head 138 thereby causing the pivoting locking leg 116
to pivot on pivot pin 131 from a locked position to an unlocked
position the purpose of which will become apparent in the
foregoing.
A spring 132 acting between adapter body 82 and the outwardly
extending member 120 of the pivoting locking leg 116, returns the
pivoting locking leg 116 to the locked position when the actuating
pin returns and disengages the pivoting locking leg 116.
A set screw 128 is provided in body 118 of the pivoting locking leg
116 to allow the locking position of the pivoting locking leg 116
to be fine tuned and adjusted.
A colored insert 130 is provided on the surface of the adapter body
82 for the purpose of identifying the particular size of the cup
adapter 80. As mentioned earlier, the cup adaptor is sized to
correspond to a particular sized acetabular cup assembly.
FIG. 4B shows the adapter body 82 without the pivoting locking leg
116 installed. As can be seen, a bore 110 is provided in the
adaptor body 82 and communicates with smaller bore 106. The larger
diameter of bore 110 allows the actuating pin 134 to be assembled
into the adapter body while also providing a space for linear
reciprocating motion of the head of the actuating pin 134 within
the adaptor body 82 as will be explained further on.
Also visible in FIG. 4B is one of the outwardly extending members
87A of split leg 86 and its associated track coupling section 93A
and track coupling groove 95A. Further, recess 112 is provided in
outwardly extending member 85 for the purpose of receiving the
earlier mentioned indicia insert 130.
In FIG. 4C, there is shown an enlarged illustration of the pivoting
locking leg 116. The body 118 of the pivoting locking leg 116
includes a threaded bore 126 for receiving the set screw 128.
Disposed on the opposite side of body 118 is an aperture 128 which
receives pivot pin 131. The outwardly extending member 120 of
pivoting locking leg 116 includes a spring seat 124 for receiving
the pivoting locking leg return spring 132. At the free end of
locking pin 122 is radiused at 123.
In FIGS. 4D and 4E, the outwardly extending member 85 and the track
coupling section 88 of leg 84 form a generally T-shape structure.
The track coupling 88 section forms an arc-like member. In FIG. 4D,
the track coupling groove 90 extends in an arc-like manner and is
shown in phantom by broken lines.
Similarly, split leg 86 and track coupling section 92 form a
generally T-shape structure. The outwardly extending member 120 of
the pivoting locking leg 116 is disposed between outwardly
extending members 87A and 87B as shown in FIGS. 4D-4F. The track
coupling sections 95A, 95B and locking pin 122 of pivoting locking
leg 116, form an arc-like profile which is substantially identical
to the arc-like profile of track coupling section 88. Further, the
track coupling grooves 93A and 93B both extend in an arc-like
manner in each of their respective track coupling sections as shown
in phantom by the broken lines.
A slot 83, for receiving the body 118 of pivoting locking leg 116,
is provided in a portion of the adaptor body 82 located immediately
adjacent to the head 138 of the actuating pin 134 and communicates
with bores 106 and 110 as shown in any of FIGS. 4D, 4F and 4G.
Flats 140A and 140B are provided on the adaptor body 82 in the area
immediately adjacent to the base of the cylindrical member 98 as
shown in any of FIGS. 4E, 4F or 4G. The function of these flats
will soon become apparent.
As already mentioned, the present invention also consists of a
specially designed impactor tool. When the impactor tool is used in
conjunction with the earlier-described cup adaptor, it allows the
surgeon to accurately position the acetabular cup of the present
invention within the acetabulum and then drive the acetabular cup
into place.
A preferred embodiment of the impactor tool hereinafter referred to
as "IPT", will now be described with reference to FIGS. 5A-5E. It
should become apparent to one of ordinary skill in the art,
however, that many variations in the structure of the impactor are
possible depending upon factors such as, the particular
configuration of the cup adaptor, etc.
Referring first to FIG. 5A, the IPT according to the present
invention is designated by the numeral 150. The IPT 150 generally
comprises a tubular shaft 152 having a first end and second end.
The first end includes a chuck coupling means 154 having a
reciprocating chuck release collar 156 and a collar grip 170.
The second end of the tubular shaft 152 comprises a hand grip 172
and a reciprocating cup release collar 174. Both the release collar
156 and the cup release collar are biased in the direction of the
first end. IPT 150 further comprises an assist handle assembly 176
which is angularly attached to the tubular shaft immediately
adjacent to cup release collar 174. The assist handle assembly
comprises an assist handle shaft 178 having a grip 180 on one end
and a tapered coupling 182 on the other end. The assist handle is
removably attached to the tubular shaft 152 via assist handle
receiving collar 184.
As shown in FIGS. 5B-5D, coupling means 154 comprises the free end
158 of tubular shaft 152 and includes anti-rotation keys 159A and
159B. A stepped bore 160 for receiving the cup adaptor chuck is
provided in free end 158. Just beyond the stepped bore 160 in the
marginal end of tubular shaft 152 are opposing locking ball
apertures 166A and 166B. Apertures 166A and 166B receive locking
balls 164A and 164B. The locking balls are held in the apertures by
the chuck release collar 156 and a cup release rod 162. The cup
release rod 162 extends through the tubular shaft 152 and couples
with the cup release collar 174. An annular inclined inner surface
168 is provided at the free end of the chuck release collar
156.
A preferred method for installing the acetabular cup of the present
invention using the impactor tool and cup adaptor of the present
invention will now be described.
First, an appropriately sized acetabular cup is selected and then
an appropriately sized cup adaptor is selected. The IPT is then
coupled to the selected cup adaptor. To couple the cup adaptor to
the IPT, one merely grasps and slides the collar grip 170 along the
tubular shaft 152 in the direction of the hand grip 172 as shown in
FIG. 5C. At the same time, the chuck 96 of the adaptor cup is
inserted into the stepped bore 160 of the IPT. This causes the
locking balls to engage chamfered edge 104 of locking flange 102
and travel through their respective locking ball apertures. The
balls pass partially through the apertures into the space provided
by the inclined inner surface 168 of the chuck release collar. When
the cylindrical collar 98 is fully seated within stepped bore 160,
the chuck release collar is released and snaps back to its original
position. As the collar moves back to its original position, the
inclined surface 168 forces the locking balls back through their
apertures into groove 100 on the chuck of the cup adaptor thus
locking the cup adaptor and IPT together. When fully coupled, the
anti-rotation keys 159A and 159B of the IPT mate with flats 140A
and 140B on the cup adaptor to prevent the IPT from rotating
relative to the cup adaptor.
Once the cup adaptor and IPT are coupled together, the cup adaptor
is coupled to the selected acetabular cup. The acetabular cup and
cup adaptor are locked together by turning the cup adaptor along
the base surface 28 of the cup so that the tracking coupling
sections 90 and 92 of the cup adaptor run along the locking tracks
42A and 42B of the cup and lock into place in a bayonet locking
arrangement as shown in sequence in FIGS. 6A-6D. Note that only the
track coupling section 92 having the pivoting locking arm is shown
in FIGS. 6A-6D. It should be understood, however, that track
coupling section 90 engages its associated locking track 42B in
virtually the same manner except for the operation of the locking
pin.
Accordingly, as track coupling section 92 engages locking track
42A, undercut inner surface 50A coacts with groove portion 94 as
shown in FIG. 6D, to prevent axial separation of the cup from the
cup adaptor. In FIGS. 6A and 6C, track receiving section 92 slides
along locking track 42A.
Upon engagement, as seen in FIG. 6A, the locking pin 122 of the
pivoting locking arm begins to ride up the inclined surface 49A
from base surface 28. As locking pin 122 rides up the inclined
surface 49A, the pivoting locking leg pivots into the unlocked
position and compress the pivoting leg return spring.
In the sequence shown in FIG. 6B, the locking pin 122 has completed
its movement up inclined surface 49A and is now riding along track
rim surface 46A. At this point, the pivoting locking leg has fully
pivoted into the unlocked position.
In the final sequence shown in FIG. 6C, the locking pin 122 moves
into depression 44A. This occurs, when the pivoting leg return
spring forces the pivoting locking leg back into the locked
position thereby causing the locking pin 122 to move into
depression 44A. Once pivoting pin 122 is in depression 44A, the cup
adaptor can not be rotated relative to the cup. The fully coupled
acetabular cup/cup adaptor/IPT assembly can be seen in FIG. 7A.
The acetabular cup, using the impactor, is placed at the entrance
to the acetabular socket where the alignment of the cup is checked
and confirmed using the impactor. Once alignment and position are
established, the acetabular cup is impacted into the acetabulum
using a mallet (not shown) on the end of handle grip of the
impactor.
Once the acetabular cup is fully seated within the acetabulum, the
cup adaptor is uncoupled for the acetabular cup. In order to
release the cup from the cup adaptor, one slides the cup releasing
collar toward the first end (coupling end) of the IPT as shown in
FIG. 7B. This causes the cup releasing rod to engage and move the
actuating pin of the cup adaptor which thereby pivots the pivoting
arm into the unlocked position such that the locking pin is no
longer seated in the depression. The cup adaptor and IPT are then
rotated relative to the cup along the base surface until the track
receiving sections disengage from the locking tracks of the cup.
Once disengagement occurs, the cup adaptor/IPT can be removed from
the acetabular cup.
To release the cup adaptor from the IPT, one merely slides the
retaining collar 156 of the IPT toward the hand grip while removing
the chuck of the adaptor assembly from the coupling means.
Although the preferred embodiments of the acetabular cup 10, the
adaptor cup 80 and the impactor tool 150 described above are
designed to replace the human hip acetabulum, modifications of
these devices to render them suitable in other applications such as
the shoulder or the like, will become apparent to those skilled in
the art.
Thus, these and other variations or modifications to the invention
described herein are intended to be included within the scope of
the invention as defined by the appended claims.
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